1. Field of the Invention
The present invention relates to a power transmission apparatus and a power transmission system which transmit electric power without contact.
2. Description of the Related Art
For electric power supply to wearable devices, such as a watch, and electric vehicles etc., power transfer systems for transferring electric power without contact are used in recent years. In such power transfer systems, an electromagnetic field generated by passing a current through a coil on a power transmission apparatus side (i.e., power transmission coil) is used to transfer power to a coil on a power reception apparatus side (i.e., power reception coil). In order for the power reception coil to capture a lot of magnetic flux of the magnetic field generated by the power transmission coil, the power transmission coil and the power reception coil are often arranged in parallel and opposed to each other.
To capture a lot of magnetic flux from the power transmission coil, the opening of the power reception coil is desirably formed to have a large area. If the power reception apparatus is a device such as a watch, the power reception coil is usually mounted in parallel with the dial so that a lot of magnetic flux from the power transmission coil is captured (for example, Japanese Patent Application Laid-Open No. 2005-160253).